Apparatus for and process of oxidizing lead bullion containing precious metals



(No Model.) J. TUNBRIDGE.

APPARATUS FOR AND PROCESS OF OXIDIZING LEAD BULLION CONTAINING PRECIOUS METALS.

No; 252,817. Patented Jan. 24,1882.

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UNHTED STATES JOHN TUNBRIDGE, ossnwanx, NEW JERSEY.

APPARATUS FOR AND PROCESS OF OXIDIZlNG LEAD BULLION CONTAINING PRECIOUS METALS.

SPECIFICATION forming part of Letters Patent No. 252,817, dated January 24, 1882. Application filed Apr-i113, 1881. (No model.)

T 0 all whom it may concern Be it known that'I, JOHN TUNBRIDGE, of Newark, in the county of Essex and State of New Jersey, have invented a new and Improved Apparatus for and Process of Onpellating or Oxidizing Lea-d Bullion Containing Precious Metals, of which the following is a specification.

Figure 1 is a plan or top viewot' my 'im proved oxidizing apparatus. Fig. 2 is a vertical central section of the same.

This invention relates to anew apparatus for charging molten lead bullion, which contains gold or silver, with oxygen, in a heated condition, for the purpose of oxidizing the lead and gaining the gold or silver; and the invention involveslikewise the employmentof a new process, which consistsin forcing the oxygen, in a heated condition, into the lower part of the vessel that contains the molten lead bullion, so that the heated oxygen will be forced to permeate the entire column of the liquid metal, and to pass up through said column in small bubbles, serving therefore to thoroughly oxidize the lead, and causing the separation therefrom of the silver, on the principle well known in the art of cupellation.

The ordinary cupellation process consistsin causing a current of air to play over the surface of the mixed silver or precious metal and lead, and thus to gradually oxidize the lead, leaving the silver or other precious metal free; but the said process takes a greatdealof time, in the first place, and in the second place fails to reach all the particles of lead, and is therefore applicable only to shallow muffles in which nearly the whole of the molten mixture is exposed at the surface. My invention differs from this by forcing the oxygen, in heated condition, either pure or as usually mixed with the atmosphere, through the molten column of mixed lead and precious metal that is contained in a suitable pan.

In the accompanyingdrawings. the letterA represents the pan. The same is suspended over a suitable furnace, B, and into it dips, so as to reach nearly to the bottom, the open end of a pipe, D. The pipe D connects, in suitable manner, with a fan or other air-propelling apparatus, E, and has ajoint, asshown at a, so that it can be turned out of the pan, as indicated by dotted lines in Fig. 2. The mixture of lead and precious metal is first placed into the pan and subjected to the heat of the furnace until the lead is at a lively redheat, and when properly melted the air or oxygen blast is made to pass through the pipe D into the lower part of the column of molten metal. The lower end or discharge end of the pipe D may have a rose attached to it, so as to discharge the oxygen in fine jets into the molten metal and insure a more thorough distribution of its particles among the particles of metal. The oxygen will pass up through the molten metal in form of bubbles, and will on its way thoroughly oxidize the lead, causing it to become separated from the precious metal. The air or oxygen that passes through the pipe D is heated to about 700 Fahrenheit, which is more than the melting-point of lead, but less than the melting-point of silver or gold. This heated oxygen enters the pan, and may be heated by passing the pipe D through a chamber, F, of the furnace, through which the products of combustion from the furnace B escape on their way to the chimney. The heated oxygen that is forced into the pan A combines rapidly with the molten lead and forms oxide of lead, which, being lighter than lead, will float on the s rt'ace of the contents of the pan, and will gradually allow the gold or silver. by their greater specific gravity, to become liberated and drop to the bottom of the pan. Hence it will be seen that the old process of blowing a current of oxygen over the surface of the contents of the pan cannot be thorough, inasmuch as that upper surface will soon become a mere surface of oxide of lead, preventing the current from reaching the remainder of the surface, unless provision is made for keeping the lead in constant motion, or for rapidly taking away the upper stratum of oxide of lead. By my process, however,the entire contents of the pan can be properly oxidized or scoritied or cupellated, according to the size of the apparatus, without disturbing the contents of the pan at any time during the operation; but if desired, of course, the oxide of lead can also be removed from time to time during the operation.

I am awaie that in refining and desilverizing lead it has been customary to add zinc to the fusion of said metals, and then pass steam through them. This will cause the zinc to unite with the silver and t0 float it on top of the purified lead. My invention (litters essentially from all known processes, in that I cause the lead to become lighter than the silver and to float on top of it. This is done by oxidizin, the entire mass of molten lead, thereby making it lighter than silver.

I am also aware that cold air has been blown through molten lead to crystallize and refine it;

I), having joint a, and with the propelling apparatus E, all arranged to permit oxygen to be heated and forced into the lower part of said pan when the latteris filled with molten metal, substantially as described.

I 2. The process herein described of oxidizing all the lead contained in the mixtures of lead and precious metals by forcing into such mixtures, while they are in a molten condition, a current of superheated oxygen, and causing the same to ascend through the molten mixture, thereby producing oxide of lead that will float on top of the precious metal, substantially as described.

JOHN TUNBRIDGE.

Witnesses:

JoHN O. TUNBRIDGE, WILLY G. E. ScIIUL'rz. 

